Differential Antimicrobial Effect of Essential Oils and Their Main Components: Insights Based on the Cell Membrane and External Structure

Synergistic Polymer Coatings with Antibacterial and Antiviral Properties for Healthcare Applications

The role of frequently touched surfaces in the transmission of infectious diseases is well-documented, and the urgent need for effective surface technologies with antipathogen activity has been highlighted by the recent global pandemic and rise in antimicrobial resistance. Here, we have explored combinations of up to 3 different classes of compounds within a polymeric matrix to enable the fabrication of coatings with broad-spectrum activity. Compounds were either based on metals or metal oxides, namely, copper, silver, and copper oxide, essential oils, namely, cinnamaldehyde, tea tree oil, and carvacrol oil, or cationic polymers, namely, poly(ε-lysine) and poly(hexamethylene biguanide). These compounds were mixed into a polymer matrix, coated, and dried to yield durable coatings. Coatings containing up to 7.5% (w/w) of the compounds were assessed in the zone of inhibition and biofilm assays using Staphylococcus aureus and Pseudomonas aeruginosa, as well as infectivity assays using human coronavirus OC43. Our data demonstrate that a selected combination of additives was able to provide a 5-log reduction in the colony-forming units of both bacteria and a 4-log reduction in viral infectivity. This simple but highly effective technology is expected to find applications in environments such as hospitals, aged care facilities, or public transport.

Phytochemical Analysis of Centaurea calcitrapa L. Aerial Flowering Parts Serial Solvent Extracts and Its Antibacterial and Antioxidant Activities

To evaluate the phytochemical composition, antibacterial, and antioxidant activity of successive extracts of Centaurea calcitrapa L. (C. calcitrapa) aerial flowering parts, they were assessed in vitro. Using a spectrophotometer, the sample absorbance at 517 nm was used to quantify the scavenging activity. The negative control was DPPH. In the current study, the diffusion using agar wells technique was adapted to measure antimicrobial activity. Phytochemical analysis was performed using the recommended standard procedures. The methanol extract of C. calcitrapa exhibited high levels of total phenolic acids expressed as gallic acid (GA), measured as (97.25 ± 0.73 mg GAE/g) content compared to the chloroform, acetyl acetate, and aqueous extracts (27.42 ± 0.29, 64.25 ± 0.96, and 17.25 ± 0.73 mg GAE/g), respectively. Additionally, the methanol extract had a higher total tannin (27.52 ± 0.53 mg TAE/g) content compared to the chloroform, ethyl acetate, and aqueous extracts (12.02 ± 0.55, 26.01 ± 0.81, and 7.35 ± 0.56 mg TAE/g), respectively, while the aqueous extract contains a lower percentage of flavonoids (141.10 ± 1.31 mg RTE/g) compared to the higher content achieved by the methanol extract (425.93 ± 1.27 mg RTE/g). The hydroxyl groups of the flavonoid and the phenolic compounds found in C. calcitrapa are essentially scavenging free radicals. Radical scavenging activity was highest in the methanol extract (IC50 = 2.82 μg/mL), aqueous extract (IC50 = 8.03 μg/mL), ethyl acetate extract (IC50 = 4.79 μg/mL), and chloroform extract (IC50 = 6.33 μg/mL), as compared to the standard scavenging activity (IC50 = 2.52 μg/mL). The antibacterial properties of C. calcitrapa against Gram-negative bacterial strains Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, and Acinetobacter baumanii, in addition to Gram-positive strains Staphylococcus haemolyticus, Enterococcus faecalis, and Staphylococcus aureus, revealed inhibition zone diameter. The findings of this investigation establish that the aerial flowering parts of C. calcitrapa have substantial antibacterial action against human infections, and the plant can serve as a significant antioxidant that can be employed to prevent and treat severe degenerative diseases brought on by oxidative stress. qPCR showed that C. calcitrapa extracts elevate both SOD1 and SOD2 (cellular oxidation markers) with remarkable folds (1.8-fold for SOD1 and SOD2) with ethyl acetate plant extract against ascorbic acid as a control. This result reflects that C. calcitrapa extracts have remarkable antioxidant activity.

Promising effects of 1,8 Cineole to control Giardia lamblia infection: Targeting the inflammation, oxidative stress, and infectivity

Reportedly, synthetic drugs such as metronidazole, furazolidone, tinidazole, and quinacrine are used for the treatment of giardiasis but are associated with adverse effects. In this study, we aimed to investigate the in vitro and in vivo effects of eucalyptol (ECT, 1,8 cineole) alone and in combination with metronidazole (MNZ) on Giardia lamblia. The effects of ECT on cell viability, plasma membrane permeability, and gene expression levels of adenylate cyclase (AK) and extracellular signal kinases 1 and 2 (ERK1 and ERK2) in trophozoites of G. lamblia were assessed. In vivo, the effects of ECT alone and in combination with MNZ were assessed on mice infected with G. lamblia. In addition, the gene expression of inflammatory genes (e.g., TNF-α, IL-1β, and IL-10) and antioxidant genes (catalase (CAT), superoxide dismutase 1 (SOD1), glutathione peroxidase 2 (GPX2)) was determined by real-time PCR. The IC50 values of ECT, MNZ, and ECT+MNZ on trophozoites were 30.2 µg/mL, 21.6 µg/mL, and 8.5 µg/mL, respectively. The estimated Fractional inhibitory concentration index (FICI) values for ECT and MNZ were 0.28 and 0.39, respectively. The application of ECT on G. lamblia trophozoites resulted in a dose-dependent increase in plasma membrane permeability, particularly at concentrations of ½ IC50 and IC50 (P < 0.05). The treatment of infected mice with various doses of ECT, mainly in combination with MNZ for 7 days, resulted in a significant decrease (P < 0.001) in the average number and viability of cysts. ECT, especially when combined with MNZ, caused a significant (P < 0.001) reduction in the expression of TNF-α and IL-6 genes, and an increase (P < 0.05) in the expression of IL-10 genes. ECT alone and mainly in combination with MNZ leads to a significant (P < 0.001) increase in the gene expression of CAT, SOD, and GPX genes. These findings demonstrate that the use of ECT in these doses, even for 14 days, does not have any toxic effects on the function of vital liver and kidney tissues. The study findings confirmed the promising effects of ECT against G. lamblia infection both in vitro and in vivo. Considering the possible mechanisms, ECT increases plasma membrane permeability and reduces the expression levels of infectivity-related genes. In addition, ECT suppresses inflammation and oxidative stress, controlling giardiasis in mice. More studies are needed to clarify these findings.

Essential Oils against Candida auris-A Promising Approach for Antifungal Activity

The emergence of Candida auris as a multidrug-resistant fungal pathogen represents a significant global health challenge, especially given the growing issue of antifungal drug resistance. This review aims to illuminate the potential of essential oils (EOs), which are volatile plant secretions containing complex mixtures of chemicals, as alternative antifungal agents to combat C. auris, thus combining traditional insights with contemporary scientific findings to address this critical health issue. A systematic literature review was conducted using the PubMed, Scopus, and Web of Science databases from 2019 to 2024, and using the Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol to identify relevant studies on the antifungal efficacy of EOs or their components against C. auris. Of the 90 articles identified, 16 were selected for detailed review. The findings highlight the diverse mechanisms of action of EOs and their components, such as disrupting fungal cell membranes, inducing the production of reactive oxygen species (ROS), and impeding biofilm formation, suggesting that some of them may be as effective as, or better than, traditional antifungal drugs while potentially limiting the development of resistance. However, issues such as variability in the composition of EOs and a paucity of clinical trials have been identified as significant obstacles. In conclusion, EOs and their active ingredients are emerging as viable candidates for creating effective treatments for C. auris, underscoring their importance as alternative or complementary antifungal agents in the face of increasing drug resistance. The call for future research underscores the need for clinical trials and standardization to unlock the full antifungal potential of EOs against C. auris.

Chemical composition, antioxidant, antimicrobial, and wound healing effects of Trachyspermum roxburghianum (DC.) H. Wolff essential oil: An in vivo and in silico approach

ETHNOPHARMACOLOGICAL RELEVANCE

Trachyspermum roxburghianum (DC.) H. Wolff, commonly known as 'Ajamoda,' is a neglected Indian spice highly used in Ayurveda and folklore remedies as an antimicrobial for chronic wounds and discharges, along with many other disease conditions.

AIM OF THE STUDY

The objective of the study was to explore chemical composition and to investigate the antioxidant, antimicrobial, analgesic, and wound healing activities of T. roxburghianum fruit essential oil from India.

MATERIALS AND METHODS

The phytochemical characterization of the oil was determined through standard qualitative procedures and the gas chromatography-mass spectrometry (GC-MS) technique. The in vitro antioxidant aptitude was assessed by scavenging DPPH and ABTS radicals. The antimicrobial potential of the oil was investigated using the disc diffusion method, followed by the determination of minimum inhibitory concentration against Gram-positive and Gram-negative bacterial and fungal strains. The analgesic potential was evaluated using thermal and chemically induced pain models in Swiss albino mice. Wound healing was assessed in vivo, including determining wound contraction rates, histopathology, and hydroxyproline estimation, using the excision wound model in Swiss albino mice.

RESULTS

GC-MS analysis identified 55 compounds with major terpenoids, including thymol (13.8%), limonene (11.5%), and others. Substantial radical-scavenging activity was exhibited by T. roxburghianum fruit essential oil (TREO) (IC50 94.41 ± 2.00 μg/mL in DPPH assay and 91.28 ± 1.94 μg/mL in ABTS assay). Microorganisms were inhibited with low MIC (2 μL/mL for the inhibition of Staphylococcus aureus and Bacillus subtilis; 4 μL/mL against Salmonella typhi and 16 μL/mL against Candida albicans). In the cytotoxicity study, no cytotoxicity was observed on the Monkey Normal Kidney Cell line (Vero). Significant antinociceptive effects were observed (25.47 ± 1.10 % of inhibition at 100 mg/kg and 44.31 ± 1.69 % at 200 mg/kg). A remarkable rate of wound closure and epithelization, along with a marked increase in hydroxyproline content, were observed for the oil during wound healing in mice.

CONCLUSIONS

The results suggested that oil could be utilized as a potential source of wound healing therapeutics.

Evaluation of the efficacy of cinnamon oil on Aspergillus flavus and Fusarium proliferatum growth and mycotoxin production on paddy and polished rice: Towards a mitigation strategy

In the present investigation, the effect of cinnamon oil (CO) (10, 30, 50 and 70 %) on the growth rate (mm/day) and aflatoxin B1 (AFB1) and fumonisin B1 (FB1) production of Aspergillus flavus (AF01) and Fusarium proliferatum (FP01) isolates, respectively was determined at optimum water activities (0.95 and 0.99 aw) and temperatures (25, 30 and 35 °C) on paddy and polished rice grains. The results showed that the growth rate, AFB1 and FB1 production of all the fungal isolates decreased with an increase in CO concentrations on both matrices. AF01 and FP01 failed to grow under all conditions on paddy at 50 % of CO concentration whereas both fungi were completely inhibited (No Growth-NG) at 70 % of CO on polished rice. Regarding mycotoxin production, 30 % of CO concentrations could inhibit AFB1 and FB1 production in both matrices (No Detection-ND). In this study, the production of mycotoxins was significantly influenced by cinnamon oil compared to the growth of both fungi. These results indicated the promising potential of CO in improving the quality of rice preservation in post-harvest; however, further investigations should be evaluated on the effects on the qualitative characteristics of grains. Especially, the prospective application of CO in rice storage in industry scales to mitigate mycotoxin contamination need also to be further researched. Moreover, collaboration between researchers, agricultural experts, and food industry should be set up to achieve effective and sustainable strategies for preserving rice.

Effect of Cymbopogon martini (Roxb.) Will.Watson essential oil on antioxidant activity, immune and intestinal barrier-related function, and gut microbiota in pigeons infected by Candida albicans

Essential oils are potential alternatives to antibiotics for preventing Candida albicans (C. albicans) infection which is responsible for economic losses in the pigeon industry. Cymbopogon martini essential oil (EO) can inhibit pathogens, particularly fungal pathogens but its potential beneficial effects on C. albicans-infected pigeons remain unclear. Therefore, we investigated the impact of C. martini EO on antioxidant activity, immune response, intestinal barrier function, and intestinal microbiota in C. albicans-infected pigeons. The pigeons were divided into four groups as follows: (1) NC group: C. albicans uninfected/C. martini EO untreated group; (2) PC group: C. albicans infected/C. martini EO untreated group; (3) LPA group: C. albicans infected/1% C. martini EO treated group; and (4) HPA group: C. albicans infected/2% C. martini EO treated group. The pigeons were infected with C. albicans from day of age 35 to 41 and treated with C. martini EO from day of age 42 to 44, with samples collected on day of age 45 for analysis. The results demonstrated that C. martini EO prevented the reduction in the antioxidant enzymes SOD and GSH-Px causes by C. albicans challenge in pigeons. Furthermore, C. martini EO could decrease the relative expression of IL-1β, TGF-β, and IL-8 in the ileum, as well as IL-1β and IL-8 in the crop, while increasing the relative expression of Claudin-1 in the ileum and the crop and Occludin in the ileum in infected pigeons. Although the gut microbiota composition was not significantly affected by C. martini EO, 2% C. martini EO increased the abundance of Alistipes and Pedobacter. In conclusion, the application of 2% C. martini EO not only enhanced the level of antioxidant activity and the expression of genes related to intestinal barrier function but also inhibited inflammatory genes in C. albicans-infected pigeons and increased the abundance of gut bacteria that are resistant to C. albicans.

HPLC and GC/MS analysis of Prunus ulmifolia Franch. (syn. Aflatunia ulmifolia (Franch.) Vassilcz.) leaves growing in South-Eastern Kazakhstan

Prunus ulmifolia Franch. (Rosaceae) was investigated for its phytochemical composition from South-Eastern Kazakhstan for the first time. HPLC analysis confirmed rutin (0.88%) in ethanol extract, and the extract also exhibited antioxidant activity. The GC/MS analysis identified total 44 components from main groups e.g. oxygenated monoterpenes (51.06%), oxygenated sesquiterpenes (20.33%), non-terpene derivatives (18.71%), and sesquiterpene hydrocarbons (7.89%), and the maximum content was of acyclic alcoholic monoterpenoid citronellol (36.58%). The hierarchical cluster analysis (HCA) from previous reports and present study was used to demonstrate the variations between essential oil compositions in different Prunus species. It formed three main clusters, cluster I consisted of species with benzaldehyde as dominant component. Cluster II included plants with benzaldehyde as secondary component, and cluster III was of P. ulmifolia in which benzaldehyde was not detected. Further, the essential oil was assessed for cytotoxic and antimicrobial activities too, and it showed better cytotoxic but poor antimicrobial activities.

Essential oils on the control of fungi causing postharvest diseases in mango

The use of fungicides in the postharvest treatment of mangoes has been widespread due to the incidence of pathogens, but awareness of the health risks arising from their use has increased, driving the search for more sustainable treatments. This study aimed to evaluate the activity of antifungal treatment of seven essential oils (EO) against four fungi that cause postharvest diseases in mangoes and define the minimum inhibitory concentration (MIC) and chemical composition, analyzed by gas chromatography (GC-MS). The results showed that the EOs of oregano, rosemary pepper, cinnamon bark, and clove inhibited 100% of the mycelial growth of the studied pathogens, with MIC ranging from 250 to 2000 μL.L-1. The main compound found in oregano was carvacrol (69.1%); in rosemary and pepper oil, it was thymol (77.2%); cinnamaldehyde (85.1%) was the main constituent of cinnamon bark, and the eugenol (84.84%) in cloves. When evaluating the antifungal activity of these compounds, thymol and carvacrol showed greater inhibitory activity against fungi. Therefore, this study showed the great potential of oregano, clove, rosemary pepper, and cinnamon bark essential oil as alternative treatments to synthetic fungicides in controlling postharvest diseases in mangoes.

Effects of essential oils on economically important characteristics of ruminant species: A comprehensive review

Essential oils derived from plants can provide biological impacts to livestock species. Scientific studies researching essential oils in livestock have investigated various essential oils for prevention and treatment of microbial infection and parasites as well as to enhance milk production, animal performance and rumen function. Despite the availability of several commercial products containing essential oils to promote animal health and production, the vast amount of essential oils, modes of application, and effective concentrations of the essential oils suggest there are more opportunities for essential oils to be utilized in commercial livestock production and veterinary medicine. The objective of this review is to contribute to the understanding of the value that essential oils can provide to the ruminant diet and to examine the biological impact of various essential oils on economically important production traits of ruminant species.

Effects of Supplementation with Oregano Essential Oil during Late Gestation and Lactation on Serum Metabolites, Antioxidant Capacity and Fecal Microbiota of Sows

A total of 20 healthy white × landrace sows were evenly and randomly divided into two groups, and fed basal diets unsupplemented or supplemented with 500 g/t Meriden-Stim® from day 100 of gestation until day 21 of lactation. Serum and fecal samples were collected from the sows on the final day for subsequent analysis. Compared to the control group, there were no significant differences in the sows' performances; however, an increase was observed in the piglets' weight at weaning (p = 0.08). Moreover, oregano essential oil (OEO) significantly reduced the levels of urea (UREA) (p < 0.01), total cholesterol (TC) (p < 0.05), low-density lipoprotein (LDL-C) (p < 0.05) and alanine aminotransferase (ALT) (p < 0.05) in serum. In terms of antioxidant indexes in serum, the catalase (CAT) and glutathione (GSH) levels showed significant increases (p < 0.05) while the malondialdehyde (MDA) level exhibited a decrease tendency (p = 0.09). 16S rRNA analysis identified the specific bacteria taxa in feces. OEO significantly decreased the relative abundance of Proteobacteria and Actinobacteria at the phylum level (p < 0.05). At the genus level, OEO significantly increased the relative abundance of Lactobacillus and Prevotellaceae UCG 003 and UCG 005, while decreasing that of Escherichia-Shigella (p < 0.05). Taken together, OEO supplementation in maternal diets during late gestation and lactation improved serum metabolites, antioxidant capacity and regulated the intestinal-flora balance of sows, thereby tending to increase the piglets' weight at weaning.

The efficient activity of plant essential oils for inhibiting Botrytis cinerea and Penicillium expansum: Mechanistic insights into antifungal activity

Botrytis cinerea and Penicillium expansum produce deterioration in fruit quality, causing losses to the food industry. Thus, plant essential oils (EOs) have been proposed as a sustainable alternative for minimizing the application of synthetic fungicides due to their broad-spectrum antifungal properties. This study investigated the efficacy of five EOs in suppressing the growth of B. cinerea and P. expansum and their potential antifungal mechanisms. EOs of Mentha × piperita L., Origanum vulgare L., Thymus vulgaris L., Eucalyptus globules Labill., and Lavandula angustifolia Mill., were screened for both fungi. The results showed that the EO of T. vulgaris and O. vulgare were the most efficient in inhibiting the growth of B. cinerea and P. expansum. The concentration increase of all EO tested increased fungi growth inhibition. Exposure of fungi to EOs of T. vulgaris and O. vulgare increased the pH and the release of constituents absorbing 260 nm and soluble proteins, reflecting membrane permeability alterations. Fluorescence microscopic examination revealed that tested EOs produce structural alteration in cell wall component deposition, decreasing the hypha width. Moreover, propidium iodide and Calcein-AM stains evidenced the loss of membrane integrity and reduced cell viability of fungi treated with EOs. Fungi treated with EOs decreased the mitochondria activity and the respiratory process. Therefore, these EOs are effective antifungal agents against B. cinerea and P. expansum, which is attributed to changes in the cell wall structure, the breakdown of the cell membrane, and the alteration of the mitochondrial activity.

Exploring the potential of 1,8-cineole from cardamom oil against food-borne pathogens: Antibacterial mechanisms and its application in meat preservation

Food-borne pathogenic bacteria are a major public health concern globally. Traditional control methods using antibiotics have limitations, leading to the exploration of alternative strategies. Essential oils such as cardamom possess antimicrobial properties and have shown efficacy against food-borne pathogenic bacteria. The utilization of essential oils and their bioactive constituents in food preservation is a viable strategy to prolong the shelf-life of food products while ensuring their quality and safety. To the best of our knowledge, there are no studies that have utilized 1,8-cineole (the main active constituent of cardamom essential oil) as a preservative in meat, so this study might be the first to utilize 1,8-cineole as an antibacterial agent in meat preservation. The application of 1,8-cineole had a significant suppressive impact on the growth rate of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella Typhimurium in meat samples stored for 7 days at 4 °C. Additionally, the surface color of the meat samples was not negatively impacted by the application of 1,8-cineole. The minimum inhibitory concentration was 12.5-25 mg/ml, and the minimum bactericidal concentration was 25-50.0 mg/ml. The bacterial cell membrane may be the target of cardamom, causing leakage of intracellular proteins, ATP, and DNA. The obtained data in this study may pave a new avenue for using 1,8-cineole as a new perspective for dealing with this problem of food-borne pathogens and food preservation, such as meat.

Biogenic silver nanoparticles and cinnamaldehyde as an effective sanitizer for fresh sweet grape tomatoes

This study evaluated the antibacterial activity of cinnamaldehyde (CIN) and biogenic silver nanoparticles (BioAgNP), alone and in combination, against Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus in vitro. Their sanitation activities on fresh sweet grape tomatoes were also evaluated. CIN and BioAgNP inhibited the growth of the tested bacteria, and at low concentrations, their combinations presented a synergistic effect. In the sanitization of fresh sweet grape tomatoes, CIN (156 µg/mL) combined with BioAgNP (31.25 µM) at subinhibitory concentrations inhibited the growth of E. coli after only 5 min of contact. Exposed samples showed no growth of E. coli during their shelf life. The combination of these compounds did not change significantly (p > 0.05) the physicochemical properties of sweet grape tomatoes and showed that CIN combined with BioAgNP could represent an effective method for decontaminating fruits and vegetables. This combination has great potential for application in the prevention of foodborne diseases.

In vitro and Quantitative and Structure Activity Relationship (QSAR) evaluation of the antifungal activity of terpenoid constituents of essential oils against Alternaria alternata and Fusarium oxysporum

INTRODUCTION

Fungal genera Alternaria and Fusarium include human and plant pathogenic species. Several antifungals have been used for their control, but excessive use has contributed to resistance development in pathogens. An alternative to searching for and developing new antifungal agents is using essential oils and their main components, which have biological activities of interest in medicine and food production.

OBJECTIVE

To evaluate in vitro and in silico the antifungal activities of terpenoids against Alternaria alternata and Fusarium oxysporum.

MATERIALS AND METHODS

The minimum inhibitory concentration and minimum fungicidal concentration values of 27 constituents of essential oils used against Alternaria alternata and Fusarium oxysporum were evaluated in vitro. In addition, using genetic algorithms, quantitative models of the structure-activity relationship were used to identify the structural and physicochemical properties related to antifungal activity.

RESULTS

The evaluated compounds proved to be effective antifungals. Thymol was the most active with a minimum inhibitory concentration of 91.6 ± 28.8 μg/ml for A. alternata and F. oxysporum. Quantitative structure-activity relationship models revealed the octanolwater cleavage ratio as the molecular property, and the phenols as the main functional group contributing to antifungal activity.

CONCLUSION

Terpenoids exhibit relevant antifungal activities that should be incorporated into the study of medicinal chemistry. Inclusion of in silico assays in the in vitro evaluation is a valuable tool in the search for and rational design of terpene derivatives as new potential antifungal agents.

Analysis of the Antibacterial Properties of Compound Essential Oil and the Main Antibacterial Components of Unilateral Essential Oils

Plant essential oils are widely used in food, medicine, cosmetics, and other fields because of their bacteriostatic properties and natural sources. However, the bacteriostatic range of unilateral essential oils is limited, and compound essential oil has become an effective way to improve the antibacterial properties of unilateral essential oils. In this study, based on the analysis of the antibacterial properties of Chinese cinnamon bark oil and oregano oil, the proportion and concentration of the compound essential oil were optimized and designed, and the antibacterial activity of the compound essential oil was studied. The results showed that the antibacterial activity of Chinese cinnamon bark oil was higher than that of oregano oil. The compound essential oil prepared by a 1:1 ratio of Chinese cinnamon bark oil and oregano oil with a concentration of 156.25 ppm showed an excellent antibacterial activity against Escherichia coli and Staphylococcus aureus. The GC-MS results showed that cinnamaldehyde was the main antibacterial component of Chinese cinnamon bark essential oil, and carvacrol and thymol in oregano oil were the main antibacterial components.

Terpenic Constituents of Essential Oils with Larvicidal Activity against Aedes Aegypti: A QSAR and Docking Molecular Study

Aedes aegypti is a vector for the arbovirus responsible for yellow fever, Zika and Chikungunya virus. Essential oils and their constituents are known for their larvicidal properties and are strong candidates for mosquito control. This work aimed to develop a quantitative structure-activity study and molecular screening for the search and design of new larvicidal agents. Twenty-five monoterpenes with previously evaluated larvicidal activity were built and optimized using computational tools. QSAR models were constructed through genetic algorithms from the larvicidal activity and the calculation of theoretical descriptors for each molecule. Docking studies on acetylcholinesterase (AChE) and sterol carrier protein (SCP-2) were also carried out. Results demonstrate that the epoxide groups in the structure of terpenes hinder larvicidal activity, while lipophilicity plays an important role in enhancing biological activity. Larvicidal activity correlates with the interaction of the sterol-carrier protein. Of the 25 compounds evaluated, carvacrol showed the highest larvicidal activity with an LC₅₀ of 8.8 µg/mL. The information included in this work contributes to describing the molecular, topological, and quantum mechanical properties related to the larvicidal activity of monoterpenes and their derivatives.

Anti-Staphylococcal Activities of Rosmarinus officinalis and Myrtus communis Essential Oils through ROS-Mediated Oxidative Stress

Rosmarinus officinalis and Myrtus communis essential oils (EOs) are well-known for their ethno-pharmaceutical properties. In the present study, we have analyzed the chemical composition of both EOs by gas chromatography-mass spectrometry. Then we assessed their antibacterial, antibiofilm, and anti-virulence actions against the opportunistic pathogen Staphylococcus aureus. The cytotoxic effect of agents tested against this bacterium was investigated by monitoring reactive oxygen-species (ROS) generation and antioxidant-enzyme (catalase) production. Regarding the antistaphylococcal effects, our results showed antibacterial efficacy of both Eos and their combination, where the minimum inhibitory concentrations ranged between 0.7 and 11.25 mg/mL. A combination of tested agents showed the highest anti-hemolytic and anti-protease effects. Additionally, association between EOs displayed more potency against the development of biofilm performed by S. aureus, with percentage of removal reaching 74%. The inhibitory impacts of EOs on S. aureus virulence factors were discovered to be concentration-dependent. Furthermore, our results provide insight on the abilities of R. officinalis and M. communis EOs, as well as their potential in combination, to generate ROS and affect oxidative stress enzyme catalase in S. aureus, leading to their antagonistic effect against this pathogen.

Essential Oils and Terpenic Compounds as Potential Hits for Drugs against Amitochondriate Protists

The human anaerobic or microaerophilic protists Giardia duodenalis, Entamoeba histolytica, and Trichomonas vaginalis are classified as amitochondriate parasites, a group of unicellular organisms that lack canonical mitochondria organelles. These microorganisms suffered adaptations to survive in hostile microenvironments and together represent an increasing threat to public health in developing countries. Nevertheless, the current therapeutic drugs to manage the infections are scarce and often cause several side effects. Furthermore, refractory cases associated with the emergence of parasitic resistance are concerns that guide the search for new pharmacological targets and treatment alternatives. Herein, essential oils and terpenic compounds with activity against amitochondriate parasites with clinical relevance are summarized and insights into possible mechanisms of action are made. This review aims to contribute with future perspectives for research with these natural products as potential alternatives for the acquisition of new molecules for the treatment of amitochondriate protists.

Biological Membranes as Targets for Natural and Synthetic Compounds

Biological membranes are responsible for all types of regulation and compound transfer, as well as information flow between and within eukaryotic and prokaryotic cells [...].

Chemical Composition, Antioxidant, Antimicrobial and Anti-Proliferative Activities of Essential Oils of Rosmarinus officinalis from five Different Sites in Palestine

The chemical profiles of Rosmarinus officinalis L. essential oils, collected from five distinct geographical regions in Palestine, were determined using GC-MS. The major phytochemical classes of R. officinalis EOs were monoterpene hydrocarbon (24.81–78.75%) and oxygenated monoterpenoids (19.01–73.78%), with 1,8-cineole (4.81–37.83%), α-pinene (13.07–51.36%), and camphor (11.95–24.30%) being the most abundant components of the studied oils. Using the DPPH assay, the antioxidant activity of EOs revealed that EO from the Jenin region had the highest antioxidant activity, with an IC50 value of 10.23 ± 0.11 µg/mL, followed by samples from Tulkarm (IC50 = 37.15 ± 2.3 µg/mL) and Nablus (IC50= 38.9 ± 0.45 µg/mL). With MICs of 12.5, 12.5, 6.25, 6.25, and 6.25 µg/mL against MRSA, S. aureus, E. coli, K. pneumonia, and P. vulgaris, respectively, the EO extracted from the Jenin region of Palestine had the greatest antibacterial activity. Furthermore, EOs from Jenin and Nablus demonstrated stronger anti-candida action than the pharmaceutical formulation Fluconazole, with MICs of 0.781, 0.781, and 1.56 µg/mL, respectively.

Supercritical CO2 assisted extraction of essential oil and naringin from Citrus grandis peel: in vitro antimicrobial activity and docking study

The extraction of bioactive compounds, including essential oils and flavonoids, using organic solvents is a significant environmental concern. In this work, waste C. grandis peel was the ingredient used to extract essential oil and naringin by conducting a supercritical CO2 technique with a two stage process. In the first stage, the extraction with only supercritical CO2 solvent showed a significant enhancement of the d-limonene component, up to 95.66% compared with the hydro-distillation extraction (87.60%). The extraction of naringin using supercritical CO2 and ethanol as a co-solvent was done in the second stage of the process, followed by evaluating in vitro antimicrobial activity of both the essential oil and naringin. The essential oil indicated significant activity against M. catarrhalis (0.25 mg ml-1), S. pyogenes (1.0 mg ml-1), S. pneumoniae (1.0 mg ml-1). Whilst naringin gave good inhibition towards all tested microbial strains with MIC values in the range of 6.25-25.0 μM. In particular, naringin exhibited high antifungal activity against T. rubrum, T. mentagrophytes, and M. gypseum. The molecular docking study also confirmed that d-limonene inhibited bacterium M. catarrhalis well and that naringin possessed potential ligand interactions that proved the inhibition effective against fungi. Molecular dynamics simulations of naringin demonstrated the best docking model using Gromacs during simulation up to 100 ns to explore the stability of the complex naringin and crystal structure of enzyme 2VF5: PDB.

Combination Strategies of Different Antimicrobials: An Efficient and Alternative Tool for Pathogen Inactivation

Despite the discovery and development of an array of antimicrobial agents, multidrug resistance poses a major threat to public health and progressively increases mortality. Recently, several studies have focused on developing promising solutions to overcome these problems. This has led to the development of effective alternative methods of controlling antibiotic-resistant pathogens. The use of antimicrobial agents in combination can produce synergistic effects if each drug invades a different target or signaling pathway with a different mechanism of action. Therefore, drug combinations can achieve a higher probability and selectivity of therapeutic responses than single drugs. In this systematic review, we discuss the combined effects of different antimicrobial agents, such as plant extracts, essential oils, and nanomaterials. Furthermore, we review their synergistic interactions and antimicrobial activities with the mechanism of action, toxicity, and future directions of different antimicrobial agents in combination. Upon combination at an optimum synergistic ratio, two or more drugs can have a significantly enhanced therapeutic effect at lower concentrations. Hence, using drug combinations could be a new, simple, and effective alternative to solve the problem of antibiotic resistance and reduce susceptibility.

Mexican Oregano (Lippia berlandieri Schauer and Poliomintha longiflora Gray) Essential Oils Induce Cell Death by Apoptosis in Leishmania (Leishmania) mexicana Promastigotes

Leishmaniasis is a neglected vector-borne disease; there are different manifestations of the diseases and species involved, and cutaneous leishmaniasis caused by Leishmania (L.) mexicana is the most prevalent in Mexico. Currently, the drugs available for the treatment of leishmaniasis are toxic, expensive, and often ineffective; therefore, it is imperative to carry out research and development of new therapeutic alternatives, with natural products being an attractive option. In particular, oregano is a plant with worldwide distribution; in Mexico, two species: Lippia berlandieri Schauer and Poliomintha longiflora Gray are endemic. Both essential oils (EO’s) have been reported to have antimicrobial activity attributed to their main components, thymol and carvacrol. In this research, the leishmanicidal effect and mechanism of cell death induced by L. berlandieri EO, P. longiflora EO, thymol, and carvacrol in L. mexicana promastigotes were determined in vitro. Additionally, the cytotoxic activity in mammalian cells was evaluated. L. berlandieri EO presented higher leishmanicidal activity (IC₅₀ = 41.78 µg/mL) than P. longiflora EO (IC₅₀ = 77.90 µg/mL). Thymol and carvacrol were the major components of both Mexican oregano EO’s. Thymol presented higher leishmanial inhibitory activity (IC₅₀ = 22.39 µg/mL), above that of carvacrol (IC₅₀ = 61.52 µg/mL). All the EO’s and compounds evaluated presented lower cytotoxic activity than the reference drug; thymol was the compound with the best selectivity index (SI). In all cases, apoptosis was identified as the main mechanism of death induced in the parasites. The leishmanicidal capacity of the Mexican oregano EO is an accessible and affordable alternative that can be further explored.

Intracellular production of reactive oxygen species and a DAF-FM-related compound in Aspergillus fumigatus in response to antifungal agent exposure

Fungi are ubiquitously present in our living environment and are responsible for crop and infectious diseases. Developing new antifungal agents is constantly needed for their effective control. Here, we investigated fungal cellular responses to an array of antifungal compounds, including plant- and bacteria-derived antifungal compounds. The pathogenic fungus Aspergillus fumigatus generated reactive oxygen species in its hyphae after exposure to the antifungal compounds thymol, farnesol, citral, nerol, salicylic acid, phenazine-1-carbonic acid, and pyocyanin, as well as under oxidative and high-temperature stress conditions. The production of nitric oxide (NO) was determined using diaminofluorescein-FM diacetate (DAF-FM DA) and occurred in response to antifungal compounds and stress conditions. The application of reactive oxygen species or NO scavengers partly suppressed the inhibitory effects of farnesol on germination. However, NO production was not detected in the hyphae using the Greiss method. An LC/MS analysis also failed to detect DAF-FM-T, a theoretical product derived from DAF-FM DA and NO, in the hyphae after antifungal treatments. Thus, the cellular state after exposure to antifungal agents may be more complex than previously believed, and the role of NO in fungal cells needs to be investigated further.

Antibacterial Activity of Clove, Oregano, Thyme, Eucalyptus, and Tea Tree Essential Oils against Escherichia coli and Klebsiella pneumoniae strains

Background: In view of the high recurrence rate of urinary tract infections and the increasing number of germs resistant to multiple antibiotics, the aim of the present study was to evaluate the antibacterial properties of clove, oregano, thyme, eucalyptus, tea tree essential oils (EOs) against 32 isolates of Escherichia coli and 28 isolates of Klebsiella pneumoniae from patients with urinary tract infections (UTI).

Methods: The agar disk diffusion method was used to assess the susceptibility of these isolates to essential oils and the minimal inhibitory concentration (MIC), and the minimal bactericidal concentration (MBC) were determined.

Results: Our results suggest that volatile phenols (such as carvacrol in oregano EO, thymol in thyme EO, and eugenol in clove EO) are more efficacious as antibacterial than non-aromatic compounds (such as eucalyptol in eucalyptus EO and terpinene derivatives in tea tree EO).

Conclusion : The oregano EO, followed by thyme appear to have the highest efficacy against Escherichia coli and Klebsiella pneumoniae isolates investigated.

Anti-Biofilms’ Activity of Garlic and Thyme Essential Oils against Salmonella typhimurium

Biofilm control by essential oil (EO) application has recently increased to preclude biofilm production on foods and environmental surfaces. In this work, the anti-biofilm effects of garlic and thyme essential oils using the minimum inhibitory concentration (MIC) method against Salmonella typhimurium recovered from different abattoir samples were investigated along with the virulence genes (InvA, SdiA and Stn genes), and the antimicrobial susceptibility profile of S. typhimurium as well. The obtained results revealed that S. typhimurium contaminated abattoir samples to varying degrees. The InvA gene was investigated in all isolates, whereas the SdiA and Stn genes were observed in four and three isolates, respectively. Utilizing the disc diffusion method, S. typhimurium isolates demonstrated substantial resistance to most of the examined antibiotics with a high multiple antibiotic resistance index. S. typhimurium isolates demonstrated biofilm formation abilities to various degrees at varied temperatures levels (4 °C and 37 °C). In conclusion, the obtained samples from the research area are regarded as a potential S. typhimurium contamination source. Furthermore, garlic essential oil (GEO) has more potential to inhibit S. typhimurium biofilm at different sub-minimum inhibitory concentrations as compared to thyme essential oil (TEO). Therefore, these EOs are considered as potential natural antibacterial options that could be applied in food industry.

Natural Occurring Phenolic Derivatives from Mauritia flexuosa (Buriti) Stems and Their Potential Antibacterial Activity against Methicillin-Resistant Staphylococcus aureus (MRSA)

Mauritia flexuosa Linnaeus filius (buriti or aguage; Arecaceae) is a palm used by traditional medicine in Brazil to treat dysentery and diarrhea. Our group showed that the soluble dichloromethane (CH₂ Cl₂ ) fraction from EtOH extract from M. flexuosa stems inhibited the growth of methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) and it is rich in phenolic compounds. This study aimed to isolate new phenolic compounds from CH₂ Cl₂ fraction from M. flexuosa stems with in vitro antibacterial activity. The crude CH₂ Cl₂ fraction was fractionated by gel permeation chromatography (GPC) followed by semi-preparative RP-HPLC. The antibacterial activity was evaluated using the broth microdilution method against MSSA (ATCC 29213) and MRSA (clinical isolate 155). All compounds were also tested against Gram-negative (Escherichia coli; ATCC 35218) bacteria and two fungi species (Candida albicans; ATCC 14053 and Trichophyton rubrum; ATCC MYA 4438). The chemical structures of isolated compounds were determined by analysis and comparison with literature data of their NMR and HRMS spectra and optical activity. The chemical investigation yielded seven aromatic compounds, of which four, (2S,15S)-2,15-dimethyl-2,15-dioxa-1,8(1,4)-dibenzenacyclotetradecaphane (1), (2S,5S)-1-(4-hydroxyphenyl)hexane-2,5-diol (3), bruguierol E (4), and buritin (5) were previously unreported and three are known compounds identified as 6-(4'-hydroxyphenyl) hexan-2-one (2), (+)-(2R,3R)-dihydrokaempferol (6), and (+)-(2R)-naringenin (7). Compounds 1 and 7 showed antibacterial activity against MRSA and MSSA with minimum inhibitory concentrations (MICs) of between 62.5 and 31.3 μg/mL, respectively. Our preliminary findings support that CH₂ Cl₂ fraction from buriti, a typical species of flooded areas of Brazilian savanna, and its aromatic phenolic compounds are active against MSSA and MRSA contributing with understanding about the traditional use of this species.

Essential Oil Blends: The Potential of Combined Use for Respiratory Tract Infections

This study investigated the potential efficacy of 369 commercial essential oil combinations for antimicrobial, anti-toxic and anti-inflammatory activity with the aim of identifying synergy among essential oils commonly used in combination by aromatherapists for respiratory purposes. Essential oil combinations were assessed for their antimicrobial activities using a panel of Gram-positive, Gram-negative, and yeast strains associated with respiratory tract infections. The antimicrobial activity was measured by determining the minimal inhibitory concentration (MIC) of microbial growth. The fractional inhibitory concentration index (ΣFIC) was calculated to determine the antimicrobial interactions between the essential oils in the combination. The toxicity of the essential oil combinations was tested in vitro using the brine shrimp lethality assay, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on RAW 264.7 mouse macrophage cells and A549 lung cancer cell lines. In addition, an inflammatory response was evaluated measuring nitric oxide production. The essential oils, when in combination, demonstrated an increased antimicrobial effect, a reduction in toxicity and provided improved anti-inflammatory outcomes. Five distinct combinations [Cupressus sempervirens (cypress) in combination with Melaleuca alternifolia (tea tree), Hyssopus officinalis (hyssop) in combination with Rosmarinus officinalis (rosemary), Origanum marjorana (marjoram) in combination with M. alternifolia, Myrtus communis (myrtle) in combination with M. alternifolia and Origanum vulgare (origanum) in combination with M. alternifolia] were found to be the most promising, demonstrating antimicrobial activity, reduced cytotoxicity and improved anti-inflammatory effects. With the increased prevalence of respiratory tract infections and the growing antimicrobial resistance development associated with antimicrobial treatments, this study provides a promising complementary alternative for the appropriate use of a selection of essential oil combinations for use in the respiratory tract.

Bioactivity of Essential Oils for Mitigation of Listeria monocytogenes Isolated from Fresh Retail Chicken Meat

Listeria monocytogenes is one of the most severe foodborne pathogens found in several habitats. Therefore, this study aims to investigate the antilisterial activity of different essential oils (EOs) against multidrug-resistant (MDR) L. monocytogenes strains isolated from fresh chicken meat. Our results showed that the prevalence of L. monocytogenes in the examined samples was 48%. Seventy-eight isolates were identified as L. monocytogenes. Out of these, 64.1% were categorized as MDR and were categorized in 18 patterns with 50 MDR isolates. One isolate was selected randomly from each pattern to investigate their biofilm-forming ability, resistance, and virulence genes incidence. Out of 18 MDR isolates, 88.9% showed biofilm-forming ability. Moreover, the most prevalent resistance genes were ermB (72%), aadA (67%), penA (61%), and floR genes (61%). However, the most prevalent virulence genes were inlA (94.4%), prfA (88.9%), plcB (83.3%), and actaA (83.3%). The antilisterial activity of EOs showed that cinnamon bark oil (CBO) was the most effective antilisterial agent. CBO activity could be attributed to the bioactivity of cinnamaldehyde which effects cell viability by increasing the bacterial cell electrical conductivity, ion leakage, and salt tolerance capacity loss. Therefore, CBO could be an effective alternative natural agent for food safety applications.